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I the latter.

@atented Aug. 323$ men or coNcENraa'rmc I rnnoasraa cans ,itaitz JuliusBruce Ciemmer, Rolla, Ma, and Carl 0. derson, Baxter Springs, Kama,assignors to oning Mining Company, Youngstown,

Qhio, a corporation or Delaware No'mrawing. Application .iuiy 20,1938,

Serial No. 220,264

sent. (or. 209-166) tent of a flotation pulp derived from a natural toimprovements in the concentrattion of ores by flotation and isespecially directed to the recovery of fluorspar of a high degree ofpurity from ores in which it is accompanied by calcareous substances,such as calcite and other forms of calcium carbonate, and/or variousmineral sulfides such as galena (PbS) and sphalerite (ZnS).

We are aware it has heretofore been suggested that fluorspar of acidgrade, that is, containing 98% or more Cal-z, might be obtained byflotation from certain ores, for example after elaborate slime removaltreatments, but so far as we are aware no methods heretofore known areeconomicaly suitable for this purpose when the ores contain thesubstances mentioned, being inadequate to efiect suiliciently completeseparation of the calcite and/or metallic sulfides from the fluorspar toattain this'high degree of purity of Our invention relates Practicaldifilculties encountered in efi'orts to recover acid grade fiuorsparfrom calcite-bearing iluorspar ores containing metallic sulfides havethus heretofore inhibited commercial exploltation of these ores, and asour invention readily accomplishes such recovery it is consequently ofparticulai utility in relation to such ores, although it may alsoadvantageously be employed for recovery of acid grade 'fiuorspar fromfluorspar ores containing calcite and little'or no metallic sulfides ormetallic sulfides and little or no calcite. a

By extended research and experimentation we have discovered that whensuch ores, after reduction by grinding or in any other suitable mannerto sumciently finely divided condition,

for example about 100 mesh, are subjected to flotation by the ordinarymechanical operations but with certain novel reagents as hereinaftermore specifically described, fluorspar of acid grade can be recoveredwithout dimculty either directly from the ore pulp or from the tailingsremaining after preliminary flotation recovery therefrom of galenaand/or sphalerite, and a prin-' cipal object of our invention istherefore the lit lization of this discovery to provide a novel methodof recovering acid grade fluorspar from fluorspar-bearing orescontaining calcareous minerals and/or metallic sulfides, from which thefiuor- I spar must be substantially freed'to attain the requisite degreeof purity. I

A further object is the provision of a novel and economical flotationmethod for concentrating to a high degree of purity the fluorsparconduce substantially equally fiuorspar bearing ore. v

Other objects, purposes and advantages of the invention will hereinaftermore fully appear or will be understood from the .following descriptionof its practice in the production of acid grade fiuorspar from flotationpulps of various specific kinds.

One example of this practice is the production of acid grade fluorsparfrom the tailings resulting from flotation recovery of galena and sphalerite by separate operations from an Illinois ore originally containing,in addition to galena, sphalerite and fluorspar, material quantities ofcalcite and siliceous gangue, as well 'as other minor impurities. Thesetailings, the ore having been initially ground to -100 mesh, analyzed asfollows,

- Per cent Pb 0.13 Zn 0.45 CaFa 26.92 CaCOc'fl 42.90

and were pulped with water, introduced to the fluorspa'r flotationcircuit with about 1.0 lb. of oleic acid and 0.92 lb. of quebrachoextract per ton of the original dry ore, and agitated in the usualmanner with resultant production of a froth from which trate containing97.0% CaCOa. The tailings from this operation contained 6.52% Cal: and54.24% CaCOa showing a recovery in the concentrate of 81.2%of thefiuorspar content of the feed and rejection from the concentrate of98.7% of the CaCOa content of the feed. Thus while the ratio offluorspar to 09.003 in the feed was 1:1.6, we were able we secured afluorspar concen- I Cal and only 2.12%

came 97:2.12, showing the tivity of our method.

In another case, using as a feed for the fluorspar flotation circuit thefinely divided tailings after galena and sphalerite recovery from an orehaving an appreciably higher fiuorspar content and a lower calcitecontent, we were able to progood results. Thus a feed assaying 66.24%CaFz and 7.78% (32.80: was subjected to roughing and moderate cleaningin the fiuorsparfiotation circuit in the presence of 1.0 lb. of oleicacid and about 0.25 to 0.5 lb. of quebracho extract per ton of theoriginal dry ore and produced a concentrate which assayed 94.12% CaFzand 2.85% CaCOs. with a. fiuorspar recovery of 91.2% and rejection of86.2% of the calcite in the feed. The concentrate was next high degreeof selecbracho extract per ton spar content of the feed but accomplishedrejection of more than 95% of its original calcite confrom ore talingsin sued November 22, 1938, to Frederick tent, producing fluorspar of anunusually high degree of purity.

The foregoing examples demonstrate that our method'is effective torecover economically acid grade fluorspar from calcite bearing oretaillngs which are relatively rich in fluorspar and contain only a smallproportion of calcite as well as from those which are considerablyricher in calcite with a. correspondingly smaller proportion offlourspar from which it follows acid grade fluor-' spar can readily beproduced in the same way present in other proportions than those mentioned.

Our method is also effective for recovering acid grade fluorspardirectly from ore pulp before removal of the metallic sulfides andcontaining considerably greater quantities of the latter than the saidtailings. Thus an ore containing 1.75% Zn, 0.81% Pb, 84.0% Cal: and 5.0%CaCO: after grinding to --l mesh was pulped, treatedwith 1.0 lb.- ofoleic acid and 0.25 lb. quebracho extract per ton of dry feed andagitated to produce a froth. The flotation concentrate obtainedtherefrom assayed 99% CaFz, 0.03% Pb and 0.05%Zn, and the tailingscontained 3.6% Pb and 5.98% Zn; that is, 96.8% of the lead and 97.9% ofthe zinc present in the original ore were excluded from the fluorsparconcentrate recovered.

Iron sulfide is similarly rejected from fluorspar concentrates whenproduced in accordance with our method from pyrite-bearing ores, suchconcentrates containing not more than about 0.05% Fe and sometimesmaterially less than that amount.

Recovery of acid grade fluorspar by flotation can thus be effected inacordance with our method not only when the pulp treated issubstantially free from metallic sulfides but also when the lattersubstances are present in material amounts and it is also substantiallyimmaterial whether a large or a small amount of calcite is present. Ourmethod is consequently particularly advantageous in connection with oresof the type found in the important Illinois-Kentucky fluorspar area,many of which contain galena, sphalerlte and fluorspar in suchquantities that their commercial exploitation is now warranted, althoughthey have heretofore not been consideredcommercially important becauseof the unayailability of economic methods of separation andpurification.

In United States Letters Patent 2,137,600, is-

C. Abbott, Strathmore R. B. Cooke, and. Carl'O. Anderson, there isdescribed and claimed a method for removal of residual fluorine fromzinc concentrates obtained by flotation from ores of this character, topermit production of commercially useful zinc concentrates, and the saidmethod may be employed in conjunction with our method as hereindescribed to greatly enhance economic exploitation of such ore depositsthrough permitting recovery therefrom of galena and of sphalerite andflourspar of the high degrees of purity required for industrial uses.

Oleic acid, to which we have herein referred, acts as a collector forthe fluorspar in the practice of our method and as we have foun t stwhich thesesubstances are pulps and/or tailings, but many reagentsadapted for use as collectors in some non-metallic flotationmethodsheretofore practised cannot be so substituted for the reason,among others, they do not possess the requisite selectivity in view ofthe common calcium cation contained in both fluorspar and calcite.

Weconsider the ability of oleicacid to promote recovery of fluorspar inthe manner described partly due to the greater solubility of fluorsparas compared with that of calcium oleate produced by reaction betweenfluorspar and the oleic acid. However, if an attempt were made to use,instead of oleic acid, a fatty acid, the hydro carbon radical of whichis of smaller size than that of oleic acid, the esterfresulting from itsreaction with fluorspar migh be of sufficiently great solubility ascompared with that of'fluorspar to impair the selectivity of the acid asa collector and it therefore cannot be said that fatty acids generallypossess the desired qualities. Thus the reaction,

hydro-carbon radical is used.

We have also referred to the use of quebracho extract, a well knownarticle of commerce derived from trees of the genus quebracho'indigenous to the central part of the continent of South America,especially in the watersheds of the Parana and Uraguay Rivers, and abrand of this extract we have found satisfactory for the purpose namedis that now marketed as Powdered Purex Sm. Brand Quebracho Extract" bythe Tannin Corporation of New York City. This brand of the extractcontains about 71% tannin, but our invention is not limited to the useof any particular brand or to any specific tannin concentration, andwhile tannin is a major constituent of substantially all quebrachoextracts we consider reasonably suitable, tests we have made demonstratethe results we obtain are not due solely to the tannin. Thus in aneffort to duplicate by use of tannin alone a fluorspar recoverycomparable to that we have obtained as heretofore described, wesubstituted tanning for the quebracho extract and ascertained analogousresults could be obtained only by using about to times as much tanninalone as was contained in the necessary quantity of the quebrachoextract. Thus the extremely high cost of tannin per pound as comparedwith quebracho extract militates against the use of tannin alone as acollector for the fluorspar, while the greater amount of it requiredrenders it certain the results obtained by using quebracho extractcannot be attributed but in small part to the action of its tannincontent and are .obviously due in large measure to other constituents.

The extract is extremely eflective as a depressent for the calcareousand metallic sulfide constituents of the ore, and is substantiallyequally effective in eliminating siliceous materials from the fluorsparconcentrate, so that the latter when e ov r d n ac ordance with ourinvention usualwhen the feed is high 1y contains appreciably less than1% 8102 even I in siliceous materials, but as various depressants forsiliceous materials in flotation processes have heretofore been known,we do stress this property of the quebracho extract.

While we have thus far made no reference to the character of the waterwe employ, we have found it preferable to use soft water, or if onlyhard water is available, to soften it by means of a lime sodaor azeolite treatment, as the effectiveness of our method is most pronouncedand its performance most easily carried out when water of approximatelyzero hardness is used in the flotation circuit. When hard water isemployed without preliminary softening, the dissolved calcium andmagnesium salts react with the oleic acid or other collector to form anundesirable precipitate and the practice of the method then requires alarger amount of the collector than would otherwise be necessary, whilethe product may be contaminated by the precipitate and separation offiuorspar from the calcite impaired.

We also prefer to maintain the pH in the flotation circuit between 8.0and 8.6; but it is to be understood that thisrange is stated merely tofacilitate explanation of the best way we have found for constituting alimitation upon it.

We have herein described our invention with considerable particularity,especially with reference to certain examples of our practice of it inthe recovery of acid grade fluorspar, from certain specific substances,but it will of course be underwater to form a pulp, lector having afatty performing our method, and not as g stood that this is forpurposes of illustration only and is not to be considered as limiting orconfining our invention thereto; as the materials we employ therein andthose we operate upon, and the manner of carrying out the method are allsubject to variation and modification, as will readily occur to thoseskilled in the art, without departing from the spirit and scope of theinvention as defined in the appended claims.

Having thus described our invention, we claim and desire to protect byLetters Patent of the United States:

1. The method of concentrating fiuorspar ores which comprises mixing theground ore with water to form a pulp, adding to the pulp a fatty acidfluorspar flotation reagent and quebracho extract, agitating the mixtureto produce a froth and removing the froth.

2. The method of concentrating fiuorspar ores which comprises mixing theground ore with adding to thepulp a colacid radical and capable offorming a froth adapted to support fluorspar particles and a depressingagent including quebracho extract, agitating the mixture to produce afroth and removing the froth.

3. The method of concentrating fiuorspar ores which comprises mixing theground ore with water to form a pulp, adding to the pulp oleic acid anda depressing agent including quebracho extract, agitating the mixture toproduce a froth and removing the froth. I

JULIUS BRUCE CLE CARL O. ANDERSON.

